Over 40 million women in the US have reached menopause, and 40% will experience symptoms significant enough to seek medical attention. Hormone replacement therapy, prescribed to ameliorate menopausal symptoms, has been associated with an increased risk of developing breast cancer. Many women use herbal preparations for menopausal complaints, believing them to be safe. Black cohosh extract (BCE) is the largest selling herbal dietary supplement in the United States used to alleviate menopausal symptoms. The mechanism of action by which BCE acts to treat menopausal symptoms of estrogen deficiency is not clear, with some data supporting a central nervous system effect, while other studies demonstrate a proestrogenic effect. The primary aim of this study is to determine if BCE administered to symptomatic postmenopausal women results in estrogenic stimulation of the breast as measured by changes in nipple aspirate fluid (NAF) levels of estradiol, pS2, follicle stimulating hormone (FSH), leutenizing hormone (LH) and prostate-specific antigen (PSA), as well as NAF cytology. Secondary aims are to 1) evaluate if BCE saponins, the proposed active constituents in BCE, are detectable in the NAF of women receiving BCE, 2) determine if BCE leads to a reduction in clinical symptoms of menopause, and 3) determine if the biomarker effects persist after stopping BCE. As the American population ages there are an increasing number of menopausal women. Interest in herbal therapies is rapidly growing among these women, including breast cancer survivors, to treat the disruptive symptoms associated with menopause. BCE binds to the estrogen receptor and in some studies stimulates breast cells. It is therefore important to demonstrate that BCE does not increase the risk of estrogen-related cancers. We have chosen biomarkers proven to be estrogen responsive proteins which are readily measured in both NAF and blood. Although prior studies failed to correlate clinical response to BCE with changes in serum levels of LH, FSH, or estradiol, it is critical to measure these markers in the breast itself, not diluted by the contribution from other organs. The findings should allow us to design a high quality R01 submission involving a larger, randomized study of longer duration which should provide some answers on the potential role of BCE in breast cancer.